Archaeologists measure the “finger flutings” to determine the artists’ age.

The researchers suspect that eight to 10 people, including four kids aged 7 or younger, were behind the ancient finger flutings. Children left marks in every chamber. One of them was apparently just 2 or 3 years old and may have been helped by a grown-up. “The most prolific of the children who made flutings was aged around 5 — and we are almost certain the child in question was a girl,” Cooney said.

Cooney said that child’s markings appear on cave ceilings more than 6 feet (2 meters) high, which would suggest that she was held up or put on someone’s shoulders to make the marks. One chamber was so marked up by children that it may have served as a “playpen of sorts,” she said.